Proces of separating glutamic acid and other products of hydrolysis of albuminous substances from one another by electrolysis.



K. IKEDA & S. SUZUKI. PROCES-S 0F SEPARATING GLUTAMIC ACID AND OTHER PRODUCTS 0F HYDROLYSIS 0F ALBUMINOUS SUBSTANGBS FROM ONE ANOTHER B-Y ELBGTROLYSIS.

APPLICATION FILED MAY 2, 1911.

1,015,891. Patented Ja11.30,1912.

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#6594414#7 GJM/ @Mm UNITED STATES PATENT oEEicE.

KIKUNAE IKEDA AND SABUROSUK SUZUKI. OF TOKYO. JAPAN.

PROCESS OF SEPARTING GLUTAMIC ACID AND OTHER PRODUCTS OF HYDROLYSIS OF ALBUMINOUS SUBSTANCES FROM ONE ANOTHER Specification of Letters Patent.

BY' ELEeTRoLYsIs.

yateiltcd Jail. 30, 1912.

Application filed May 2, 191].. Serial No. 624,655.

To all 'wlw-m 'it may concern Be it. known that we, Ixrikixwn lunm and Samiizosukn Siizlv ii nsubjects ot thellmperor of Japan, residin, ,(T at 13 Akebonocho Hongoku and li Atagocho Nichome, Sliiba-ku, respectively, Tokyo, in the Empire, ot' Japan, have invented new and useful improvements in processes Aot' separating glutamic acid and other products of hydrolysis of albuminous substances from one another by electrolysis, otl which the following is a specitication.

Our invention relates to a process of separating the products of hydrolysis of albuminous substances by electrolysis. One

'of thc product-s, glutamic acid, has now found application on a large scale in the manufacture of lavoring, according to the present invention, and the other products will also doubtless atta-in commercial irnportance in near tuture. Methods :t'or the separation of these substances already exist which are i'ery serviceable in scientific in- Vestigations, but none of them are available for industria-l purposes. y

-The process constituting the present invention is not only a rational one for scientific purposes, but is also applicable to manufacture on a large scale, and is based upon the following considerations. AThe products ot hydrolysis of albuininous substances may be divided into three classes ot compounds, .7'. c. compounds of decidedly basic character, those ot pronounced acid nature and the neutral and amphoterie compounds whose basic and acidic properties are Very nearly balanced. To the first class belong ammonia, arginin, histidin, lysin and some other bases; to the second belong glutamic acid and aspartic acid in which monoamine-dicarboxylic acids,

acid nature preponderates greatly over the basic; while to the third class belong monoamino-nionocarboXylic acids such as glycin,

alanin, valiri, leucin, etc., which arev Very weak both as acid and base. Then a protein substance is completely hydrolyzed, there is in general an excess of basic coinpounds over those ot decidedly acid nature. Hence to make the solution perfectly neutral a part of the bases must be removed or a certain quantity of an acid must be added.

When this is done a solution is obtained` which turns both red and blue litmus paper violet on account of the amphoteric nature of ons hydrogen; the compounds ot decidedly.v

acid nature will accumulate at the anode as the salts ot' the anode metal, provided the latter of sutlicicntly strong` electropositire nature; while the weak amphoteric compounds will not partake in the electrolysis in Aan)r marked degree. lt must; therefore be possible to separate tlre coinpounds of the three classes from one another when tlie electrolysis is carried out under appropriate conditions. The isolation of each compound is then much facilitated. For example,glutamic acid can he obtaind pure troni the anodic liquid quite easily by processes which vary somewhat according to the nature ot the anodic metalv employed.

The process constitutingthe present invention is carried out as follows: The albuininous substance is best hydrolyzed by heating it with dilutev sulfuric acid, because the acid can -be most readily removed in' the foriili of calcium or barium sulfate after it not it is neutralized by careful addition of an acid, for instance hydrochloric acid. The solution is placed in an electrolytic cell, which consists of three compartments separated from one another by two diaphragins. The two outer compartments, in each of which the electrode is placed, are

made much smaller than the middle conipartment. The cathode is made of iron,

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while theanode is made of zinc, aluminium, f iron or any other metal readily soluble 1n acid. When electrolysis has been carried out for a sutticientllength of time the bases are found accumulated in the cathodic compartment, and glutamic acid, together with aspartic acid, etc., are collected in the anodic space as salts of the anode metal Awhich is used..V The greater part of the weak amvphoteric amino-acids remain in the middle vllO compartment. When the electrolysis is practically completed the solution 1n each conq'iartment 1s separately worked up? The solution in the middle compartment gives, after concentration, crystals of tyrosin and leucin, and /from the mother liquor glycocol, alanin, etc., can be obtained. The liquid in the cathodic space may be worked up for arginin, rhistdiu. etc., by proper methods, for example. by crystallization, after neutralization with picric acid. In order to isolate glutamic acid from the anodic liquid, the metal is removed as sulfate, hydroxid or carbonate. by adding hydrogen sulfid, animonia or sodium carbonate. lVhen the metal is removed as suliid the liquid becomes rather strongly acid on account of the presence of other' acids, and glutamic acid is held in solution in spite of its slight solubility in water. By careful addition of alkali, glutamic acid is precipitated in the free state; or the liquid may be saturated with hydrochloric acid and set aside for severa-l days when glutamitl acid crystalf lizes out as hydrochlorid. The latter method is also to be used when the metal has been removed as carbonate or hydroxid. The crystals of glutamic acid hydrochlorid which are generally mixed with other salts are dissolved in water, and as ymuch soda is added as is necessary to neutralize free hydrochloric acid. Glutamic acid is then precipitated as fine 'crystalline powder and van be readily purified by recrystallization.

'lhe electrolytieal separation of the products of the hydrolysis of the albuminous substances. according to the present invention, may be carried out with the aid of the apparatus shown in the accompanying drawings, in which Figure 1 is a vertical section of the apparatus, showing the three compartments hereinafter referred to; Fig. 2 is a plan view of the cathode used in the practice r of our invention; Fig. 3 is a plan view of the anode; and Fig. et is a perspective view representing the structure of the middle and cathode compartments.

Example: Glycinin obtained from the soya bean is hydrolyzed by digesting it with sulfuric acid of 2li-per cent. strength at a temperature of 10G-120o centigrade, during 6-l0 hours, and the resulting liquid is filtered from the black humus like substance. Slaked lime is added in slight excess to the liquid and the calcium sulfate produced is removed by filtration. Any sulfate in the solution is eliminated by the cautious addition of baryta water. On passing carbon dioxid through the solution and allowing to stand for some time, all calcium is precipitated as carbonate. The liquid is again filtered and is then evaporated under reduced pressure so as to drive oft' free ammonia. In this Way a very .nearly neutral solution is ling drawings.

nemesi obtained. The liquid is shaken with a little toluene 'to make it antiseptic and with this the electrolytic cell is filled. It has been found preferable to form the lelectrolytic cell into three compartments separable from one another and arranged one above the other, as is illustrated in the accompany- Such arrangement is illustrated particularly in Fig. l, wherein a rep'- resents the upper or cathodic compartment, Z the middle con'lpart-lneut, and c the lower or anodic compartment. The bottoms of the two upper compartment-s consist of a `framework d, over which strong canvas c is`stretchcd, said canvas having been previously impregnated with gelatin which is made insoluble by treatment with formaldehyde, and constituting a. diaphragm, (see particularly Fig. t). Such a diaphragm does not hinder the interdiiusion of the component-s in solution, and easily aliows the passage of the electric current, but otherwise it is water-tight. It is necessary that the diaphragms be supported by the gratings or framework d. The gratings and the outerv framework of the compartments are preferably constructed of Wood impregnated with paraffin or coal-tar. In the uppermost compartment is placed acathode f, which is constructed of iron wire gauze or of a grating formed of iron rods, the latter construction being shown particularly in Fig. 2. In the lowermost compartment is placed the anode y, constructed ot zinc., and also in the form-of a grating, as will be evident from Fig. 3. The poten'tial difference between electrodes is kept at 4 6 volts. The resistance of the cell varies of course according to its dimensions and the concentration of thesolution, and increases considerably as the electrolysis progresses. The current densitymust not be too large because then glutamic acid undergoes a peculiar change, the nature of which is not yet clearly understood. It is best to maintain the current density below one ampere per square decimeter, and in actual practice it is much less. In about 48 hours the electrolysis is practically completed. The three compartments are separated from one another and their contents are worked up in any convenient manner. In order to obtain glutamic acid from the anodic solution hydrogen sulfid is passed through it, if necessary with addition of calcium carbonate so as to keep down the acidity. The liquid is filtered from zinc suld and concentrated by evaporation. It

for the neutralization of the hydrochloric acid is added. Glutamic acid is then precipitated as a iine crystalline powder and can be readily purified by recrystallization.

-We claim l. The process of separating the products of hydrolysis of albuminoussub'stances into pounds formed, the first group consisting of compounds of decidedly basic character, the second group consisting of compounds of pronounced acid character, and the third group consisting of neutral compounds having very weak basic and acid character.

2. The process of separating the products of hydrolysis ot' albuminous substances into 4three groups of compounds, which consists in preparing an aqueous solution of the said hydrolytic products, subjecting the said solution of hydrolytic products to electrolysis in a cell divided into three compartments and containing a corrodible anode to separate the solution into groups collecting at the anode, c'athode, and intermediate space, and finally collecting the three groups of compounds formed, the first group consisting of compounds of decidedly basic character, the second group consisting of compounds of pronounced acid character and salts of the anode metal, and the third group consisting of neutral compounds having very weak basic and acid character.

3. The process of obtaining glutanic acid from the products of hydrolysis of albuminous substances, which consists in preparing an aqueous solution of the said hydrolytic products, subjecting the said solution of hydrolytic products to electrolysis in a cell divided into three compartments and containing a corrodible anode to sepa#l rate the solution into groups collecting at the anode, cathode, and intermediate space, collecting the three groups of `compounds formed, the rst group consisting of compounds of decidedly basic character, the second group consisting of compounds of pronounced acid character and salts of theanode metal, and the third group consisting of neutral compounds havin very weak basic and acid character, and ally separating the glutamic acid from the group of compounds of pronounced acid character.

4. The process of obtaining glutamic acid, which consists in hydrolyzing an albuminous substance by heating said albuminous subst-ance with sulfuric acid, filtering the liquid, removing the sulfuric acid and sulfates from the liquid, subjecting the liquid to electrolysis in a cell divided into three compartments and containing a corrodible anode to separate the liquid into groups collecting at the anode, cathode, and intermediate space, collecting the three groups of compounds formed, one of the liquid groups consisting of compounds of pronounced acid character and salts of the anode metal and containing the anodic metal salt of glutamic acid, and finally separating the glutamic acid from said group.

5. The process of obtaining glutamic acid, which consists in hydrolyzing an albuminous substance by heating said albuminous substance with sulfuric acid, filtering the liquid, removing the sulfuric acid and sulfates from the liquid, subjecting the liquid to electrolysis in a cell divided into three compartments and containing a corrodible anode to separate the liquid into groups collecting at the anode, cathode, and intermediate space, collecting the three groups of compounds formed, 011e of the liquid groupsI consisting ofcompounds of pronounced acid character and salts of the anode metal'and containing the anodic metal salts of glutamic acid, passing hydrogen suliid into the liquid, filtering and concentrating the liquid,

adding hydrochloric acid thereto, allowing to stand for several days whereby hydrochlorid of glutamic acid is obtained, and

finally separating the glutamic acid 'from said hydrochlorid.

In testimony whereof we aii'x our signatures in presence of two Witnesses. KIKUNAE IKEDA. SABUROSUKE SUZUKI. Witnesses:

H. F. HAWLEY, M. NAwLoN. 

